Coating paper



Patented Oct. 2 4, 1944 I COATING PAPER Philip S. Blickcns derl'er,Hamilton, Qhio, assignor to The Champion Paper and Fibre Company,Hamilton, Ohio. a corporation of Ohio No Drawing. Application December18, 1942,

Serial No. 469,745

.6 Claims.

This invention relatesto the manufacture of cast-surfaced coated paper.with aqueous coatings, on continuously moving casting surfaces such asendless metal belts or rotating drums.

In the manufacture of cast-surfaced coated paper on such belts or drums,it has been found that coating material tends to spread beyond the edgesof the paper web and contaminate the casting surface. In the continuouscoating and casting process the same section of the casting drum or beltpasses the same point many times and it has been found that where thecoating is on the paper it is removed from the casting surface beforefresh coating is applied but that beyond the edges of the paper webthere is nothing to remove even the relatively small amounts of coatingwhich get on the surface and that this coating therefore tends to buildup and become tightly adherent to the casting surface, fouling thesurface, renderin it unfit for use, and causing serious difficultieswhen the web shifts laterally or a wider web is to be coated. 'Suchaccumulations of coating material on the casting surface beyond theedges of the paper web also damage the press rolls, reduce the speed atwhich it is possible to operate, and otherwise interfere with thecoating and casting operations so thatv in the practice of the processit has been found that a very considerable part of the running time waslost by shut-downs for the purpos -of cleaning the edges of the castingsurface.

The primary object of the present invention is therefore to prevent thelarge losses of running time heretofore required for cleaning the edgesof the casting surfaces, by providing a method of preventing thebuilding up of adherent deposits of coating materials, etc. on thecasting surface beyond the edges of the paper web. Another object is tomake possible sustained operation at higher speeds than are otherwisepossible. An allied object of the invention is to provide a continuousprocess for maintaining the condition of the casting surface beyond theedges of the paper web during the operation of coat- 1 ing and castingcontinuous webs of paper. Other objects and advantages of the inventionwill be apparent from the following description.

Washing of the surfaces with water, I have found, is inadequate, as thecoating compositions used adhere too tenaciously to the casting surface.Application of oil films to these portions of the casting surface wastried. on the theory that" the coating material would not adhere to anoiled surface, but the oil was found to saturate the coating materialand render it water-repellant so that it could not even be wetted by thewashing water, and the cleaning operation'accordingly became even moredifficult than before.

I have now found it possible to accomplish the aforesaid objects andcontinuously maintain the condition of the casting surface beyond theedges of the paper web by a series of operations, as follows: First, anextremely thin film of a watersoluble oil, advantageously. in a ratherdilute solution e.. g. 5 to 10 per cent, is applied to said portionsofthe clean casting surface by any convenient method as by an atomizingspray. Thereafter the travel of thecasting surface with its oil-coatededges brings it to the place where the coating and paper are pressedonto the casting surface and greater or lesser amounts of coating areincidentally deposited on the oiled casting surface beyond the edges ofthe paper, web. Substantially immediately thereafter these parts of thesurface are washed by a forcible water spray which removes or floatsmost if not all of the coatin material from the oil film. The watercarrying the coating material and some of the oil film is then removedfrom the surface by a suitable air jet.

I have found .that soluble calcium or magneslum salts constitutinghardness" in this wash water, react with the sulphonated oils used, toform gummy insoluble compounds. Even if completely soft water isused,the trouble is not ordinarily avoided, because of the usual presence ofcalciumor magnesium salts in the coating materials themselves. Whentrouble from such sticky and gummy compounds is encountered, I prefer tofollow the washing and blowing operations by a series of steam jetsdirected at an angle against the surface tending to blow the defitslaterally off of the edges of the casting ace. The hot moisture of thesteam jets tends to soften these deposits so that they are blown ofi ofthe surface by the jets. Even in cases where the jets, due to impropeadjustment or to other cause, may not serve to maintain absolutecleanliness of these parts of the casting surface, the deposits areslnall in amount and relatively soft and nonadherent so that they may bereadily wiped from the surface without the necessity of the longshut-downs heretofore required for cleaning the edges of the castingsurfaces. After passing the steam jets, the surface again passes underthe atomizing oil sprays, which preferably apply a solution of the oilin distilled or soft water, and the described process is repeated. Theoperations are advantageously continuous,

and when once adjusted are substantially automatic, requiring little orno attention from the operators.

The oil used should, as hereinbefore noted, he

water soluble. Oils yielding solutions having detergent properties) areparticularly useful in maintaining the cleanliness of the surface.Sulphonated vegetable oils have been found to answer: the requirements,sulphonated castor oil having been used with particularly good eflect.It has further been found advantageous in many cases to use asulphonated oil neutralized with ammonia rather than one neutralizedwith other alkali. Oils having impurities, such as gums or resins, whichtend to accumulate and build up insoluble deposits on the surface shouldbe avoided. If hard water or coatings containing soluble calcium ormagnesium are to be used, it is desirable to choose anoil of which thecalcium and magnesium soaps are susceptible to solution or softening bythe heat and moisture of the steam jets used.

The casting surfaces are ordinarily of metal, though the present processis also useful when non-metallic casting surfaces are employed, so longas oils are used which are compatible with the material of the castingsurface.

The process when carried out as described serves to keepv the castingsurfacebeyond the edges of the paper web, free from accumulations ofcoating materials. I have found that it will also serve, when properlyadjusted, to free the surface fromaccumulations of coating materialwhich may have been allowed to build up due to the cleaning processbeing out of service or to other causes.

In accordance with the present invention the paper coating and castingprocesses can be operated continuously for much longer periods and athigher speeds than heretofore without the necessity for the frequentprotracted shut-downsformerly found necessary.

I claim:

1. In the manufacture of cast surfaced coated paper by hardening anaqueous coating on a 'moving web of paper'in intimate contact with acontinuously moving casting surface, the meth-- d of maintaining thecondition of the casting surface beyond the edges of the paper web,which comprises maintaining on said portions, of the casting'surface afilm of water-soluble oil and continuously washing from said him anycoating material which may be deposited thereon.

2. In the manufacture of cast surfaced coated paper by hardening anaqueous coating on a moving web of pa r in intimate contact with a con-7 'tinuously moving casting surface, the method of maintaining thecondition of the casting surface beyond the edges of the paper web,which comprises continuously applying a film of sulphonated vegetableoil to said portions of the mov-- ing; casting surface, then at alocation after the possibility of contamination of the surface withcoating material continuously washing said portions of the castingsurface with water.

3. The method of claim 2 in which the oil used is sulphonated castoroil.

4. In the manufacture of cast surfaced coated paper by hardening anaqueous coating on a moving web of paper in intimate contact with acontinuously moving casting surface, the method of maintaining thecondition of the casting surface beyond the edges of the paper web,which coniprises continuously applying a layer of sulphonated vegetableoil to said portions of the moving casting surface, then at a locationafter the possibility of contamination of the surface with coatingmaterial, continuously washing said'portions of the casting surface withwater, and blowing the water from said portions of the surface. 5. Themethod of claim 4 in which the oil used is sulphonated castor oil.

6. In the manufacture of-cast surfaced coated paper by hardening an,aqueous coating on a moving web' of paper in intimate contact with acontinuously moving casting surface, the method of I maintaining thecondition of the casting surface beyond the edges of the paper web,which compris s continuously applying water-soluble oil to said portions.of the moving casting surface, then at a location after the possibilityof contamination of the surface with coating material,continuously-washing said portions of the castin surface with water,blowing the water from said portions of the surface, and thereafterdirectin steam jets against'said surface at an angle directed away fromthe edges of the paper web thereon.-

PmLI'Ps. BLICKENSDERFER.

